Success! The mouse wheel is indeed functioning again in and out of native VR. Just like you said, we can interact with the panel mounted 750 with the VR mouse turned off, the problem still remains that you cannot see it. However, I have a workaround that works for me. I bound "toggle the 3d mouse cursor in vr" to a convenient button/key. I then hold the 3d mouse cursor over what I want to click on the 750, then press the key, it disappears but remains and I am then able to click. I have to toggle it each time I wish to click again, reposition, etc. It's clunky but it works for now. Hopefully, this can be fixed eventually, but it sounds from your previous statements that it's currently an issue with x-plane.
Thanks again!

As of 11.21r2 build 112101, the mouse wheel is no longer functioning in the 3D virtual cockpit (not in VR either) with the 750 activated through the plugin menu. I posted in the other thread to contribute there as well.

Release version - 11.20
Apologies for misunderstanding.
To further clarify:
I am able to use the mouse wheel in and out of VR normally with the default 430, etc.
I am able to use the mouse wheel in the normal 3D cockpit mode (looking at the monitor, not in VR) with the 750 on the panel, though the mouse cursor still disappears when over the 750.
I am able to use the mouse wheel using Flyinside VR and the 750 on the panel - using Flyinside also allows the mouse cursor to be viewable and interact with the 750 on the panel.
I am NOT able to use the mouse wheel with BOTH native x-plane VR AND the 750 activated. This includes using the mouse wheel to interact with any part of the cockpit - knobs, switches, etc. The mouse wheel will not interact with anything while in native VR and the 750 selected in the plugin menu.

Over all switches and knobs in the cockpit while in VR and with the 750 active. The moment I disable the 750 (and stay in VR), mouse wheel function returns. Also, when I am in normal 3D cockpit (not in VR) and 750 active, the mouse wheel works. It is only with both the 750 active and in native VR that the mouse wheel function will not interact.
Not the pop up window, this is solely with the 750 installed on the panel itself.

Thank you for your reply and for the work you all are putting into this!
I have tried testing the different settings to see if there was perhaps something in the plugin causing the mouse wheel issue, but have not found it.
If only there were a way to see the normal mouse, even as a dot, in VR, then we could see and click as I mentioned above. I tried using mouse trails, but that just renders the mouse cursor invisible in x-plane, apparently an old issue that's been around for years.
Edit: Flyinside just put out an update which now works with x-plane 11.2. I am now able to interact with the panel mounted 750 in VR and use all of the mouse functions!

Thank you for making such a wonderful addition. Our flying club has recently added the GTN 750 and 650 to one of our planes and I am hoping to use this to help become more familiar with it within the sim.
My hope is to be able to use this fully in VR without needing to use the popout windows. In the little bit of searching I have done, I realize there is some limitation with how x-plane 11 currently uses the VR mouse cursor and that it is unable to interact with the the current GTN 750/650.
What is the current status of this implementation and do you foresee being able to enable this in the future?
Does anyone know of a workaround to be able to interact with the 750 within VR (apart from the popout window)?
Also, while in VR, the mouse wheel is no longer able to control fine adjustments on knobs, mixture, etc. It works fine the moment you leave VR. This is only with the 750 enabled, the moment I disable it, the mouse wheel functions again in VR. The only plane I have tried this with is the Justflight Arrow III (non-turbo version).
Edit: I tried this in the AFM Mooney M20R Ovation II with the same results. The mouse is able to interact with the 750 in normal 3D cockpit mode and the mouse wheel works for fine control of knobs, trim, mixture, etc. Going into VR mode with VR mouse cursor, the mouse wheel no longer works and I cannot interact with the 750 on the panel. What is interesting, however, is that if I disable the VR mouse cursor, it disappears, but I can click interact with the 750 in VR mode on the panel itself. I just cannot see any cursor or what I am actually clicking (and the mouse wheel still doesn't work).